U.S. Pat. No. 4,596,030 (assigned to Carl Zeiss Stiftung) discloses a device for generating X-radiation with a plasma. This prior art device comprises two concentric cylindrical electrodes connected to a high-voltage electrical energy source with a controlled high-power switch. Formed between the electrodes is a discharge space which is closed at one end, evacuated, and filled with low-pressure gas. An insulator is arranged between the electrodes along with means for initiating a plasma discharge. This plasma shock wave is accelerated toward the open end of the discharge space and, in the region of the open end of the cylindrical inner electrode, is magnetically compressed into a plasma focus emitting X-radiation. This prior art device is operated with a gas charge or with a steady through-flow of gas. Only a single gas is used, so that both the plasma discharge and the generation of the desired X-radiation takes place in one and the same gas.
It has been found that this known device exhibits a number of disadvantages. For example, the gas used in the device must be selected so that it will create the desired plasma discharge. However, since the spectral properties of the generated X-radiation varies in accordance with the type of gas employed, the gas selected (for its plasma discharge characteristics) may produce a very low yield of X-radiation of a desired wavelength. Or, when a gas is selected to obtain a needed wavelength of X-radiation, the generation of the plasma may be less than desired.
The invention herein provides means for improving the prior art device just described above so that it can achieve optimal conditions for the creation of the plasma and for acceleration of the plasma toward the open end of the cylindrical inner electrode while, simultaneously, achieving optical conditions for generating X-radiation of the desired wavelength.